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The Zodiac Killer, one of the most notorious serial killers in history, taunted authorities and the public with cryptic ciphers for over five decades. Among these was the Z340 cipher, a 340-character cryptogram that remained unsolved for 51 years, confounding both amateur and professional codebreakers.
However, in 2020, an international team of cryptographers successfully cracked this infamous code. The details of their breakthrough and the meaning behind the message offer a fascinating insight into the mind of the Zodiac Killer and the methods used to solve this enduring mystery.
The Z340 Cipher: A Half-Century Enigma
Between 1968 and 1969, the Zodiac Killer claimed the lives of at least five people in Northern California. During his spree, he sent a series of letters to local newspapers, often accompanied by cryptic ciphers. These ciphers were intended to mock the authorities and the public, daring them to decode his hidden messages. Of the four ciphers he sent, the first, known as Z408, was cracked by amateur cryptographers Donald and Bettye Harden within days of its publication in 1969.
The Z340 cipher, however, proved to be far more challenging. Published in newspapers on Aug 06, 2025, it stumped codebreakers for over five decades. It wasn’t until December 2020 that a team of codebreakers, led by David Oranchak, Sam Blake, and Jarl Van Eycke, announced they had finally deciphered the message hidden within the Z340 cipher. Their solution was confirmed by the FBI, marking a significant breakthrough in one of the longest-standing unsolved cases in criminal history.
Cracking the Z340 Cipher: A Complex Puzzle
Decoding the Z340 cipher required an immense amount of work, computational power, and collaborative effort. The cipher used a combination of homophonic substitution, where symbols are swapped for letters, and transposition, where the letters are rearranged according to a systematic logic. While this method is not uncommon in cryptography, it left the codebreakers with hundreds of thousands of possible decryption combinations to sift through, according toThe Wrap.
To tackle the problem, the team used a specialized program called AZDecrypt, designed by Van Eycke. The program was capable of solving up to 200 homophonic ciphers per second with a 99% accuracy rate. After adjusting the software to account for the transposition aspect of the cipher, the team began making progress. It wasn’t long before they began to uncover fragments of a message that would lead them to the full solution.
The Z340 cipher revealed a chilling message from the Zodiac Killer:
“I HOPE YOU ARE HAVING LOTS OF FUN IN TRYING TO CATCH ME. THAT WASNT ME ON THE TV SHOW. WHICH BRINGS UP A POINT ABOUT ME. I AM NOT AFRAID OF THE GAS CHAMBER BECAUSE IT WILL SEND ME TO PARADICE ALL THE SOONER. BECAUSE I NOW HAVE ENOUGH SLAVES TO WORK FOR ME WHERE EVERYONE ELSE HAS NOTHING WHEN THEY REACH PARADICE. SO THEY ARE AFRAID OF DEATH. I AM NOT AFRAID BECAUSE I KNOW THAT MY NEW LIFE IS LIFE WILL BE AN EASY ONE IN PARADICE DEATH.”
The Z340 cipher message echoed the Zodiac Killer’s obsession with death and the afterlife, themes he had touched on in his earlier ciphers. His reference to “paradice” (a misspelling of paradise) and slaves for the afterlife aligned with the cryptic and delusional tone of his previous communications. One of the most striking revelations from the decoded message was the Zodiac’s claim that he had not been the person who called into a San Francisco TV show on August 06, 2025. This contradicts popular belief at the time, as many had speculated the caller was the killer himself.
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While the message contained no new leads on the Zodiac’s identity, it further solidified the profile of a deranged individual driven by dark fantasies. David Oranchak, one of the cryptographers who worked on the solution, speculated that the Zodiac may not have intended for the Z340 cipher to be as difficult to solve as it turned out to be. The complexity of the cipher might have been an unintended result of the Zodiac’s encoding process, making it nearly impossible to crack without modern computational tools.
A Legacy of Cryptic Terror
The Z340 cipher’s decryption closed a significant chapter in the long-running saga of the Zodiac Killer. While the Zodiac remains unidentified to this day, the successful cracking of the Z340 cipher highlights the determination and skill of the cryptography community. This case serves as a reminder of the enduring mysteries surrounding one of the most infamous serial killers in American history.
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The solution to the Z340 cipher stands as a testament to the power of collaboration, innovation, and persistence in the face of seemingly insurmountable challenges. Although the Zodiac Killer may never be brought to justice, the cracking of his ciphers ensures that his cryptic taunts will no longer hold their power over the public and investigators alike.
Rishabh Bhatnagar
Editor/Reviewer
Articles Published :315
Rishabh Bhatnagar is an Entertainment and pop culture journalist/editor with Fandom Wire. He has more than 6 years of experience working for multiple major platforms and is himself an avid consumer of worthwhile content. A natural storyteller, Rishabh has a unique way with words and is always looking to improve, as a storyteller, writer, and a journalist.
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